Area flood gun

ABSTRACT

An electron source is provided by thermionic filaments in the form of elongated strips or wires, such filaments being mounted within a casing. A deflector electrode is formed on a wall of the casing behind the filaments and director electrodes placed forward of the filaments in the direction in which the electron flow is desired. The various electrodes are positioned relative to the filaments and have potentials applied thereto such that uniform distribution of electrons is provided over a predetermined area over which electron flow is desired. The filaments are resiliently supported in the casing so that they are appropriately tensioned to avoid sag when they are heated, and are able to withstand shock and vibration.

United States Patent 1 1 Di Benedetto et al.

[451 Nov. 4, 1975 1 AREA FLOOD GUN [73] Assignee: Texas InstrumentsIncorporated,

Dallas, Tex.

[22] Filed: Feb. 22, 1974 [21] Appl. No.: 444,798

Stapleton et a1. 313/278 Adams, Jr 313/278 Primal ExaminerSaxfieldChatmon, Jr. Attorney, Agent, or Firml-larold Levine; James T. Comfort;Richard L. Donaldson [57] ABSTRACT An electron source is provided bythermionic filaments in the form of elongated strips or wires, suchfilaments being mounted within a casing. A deflector electrode is formedon a wall of the casing behind the filaments and director electrodesplaced forward of the filaments in the direction in which the electronflow is desired. The various electrodes are positioned relative to thefilaments and have potentials applied thereto such that uniformdistribution of electrons is provided over a predetermined area overwhich electron flow is desired. The filaments are resiliently supportedin the casing so that they are appropriately tensioned to avoid sag whenthey are heated, and are able to withstand shock and vibration.

2 Claims, 5 Drawing Figures US. Patent Nov. 4, 1975 mdE AREA FLOOD GUNThis invention relates to electron guns, and more particularly to such agun capable of distributing electrons emitted from a thermionic filamentover a predetermined area.

In US. Pat. No. 3,769,540, issued on Oct. 30, 1973, an area electronflood gun is described which utilizes a plurality of strip filaments inconjunction with appropriately positioned deflector and directorelectrodes to generate electrons which are uniformly distributed over apredetermined area. In the illustrative embodiment of the inventionshown in said patent, the filaments are mounted within a deflectorelectrode in the form of a flat dish, this deflector electrode being aseparate member which is mounted within a casing. in the device shown inthe patent, the filaments are suspended between opposite wall portionsof the dish electrode by means of filament leads which provide a smallamount of spring tensioning therefor.

It has been found that while an assembly of this type operatessatisfactorily under conditions involving little shock or vibration, itis unable to withstand high shock and vibration conditions such as, forexample, encountered in military aircraft. A highly ruggedized designhas been used to overcome this difficulty. This design, while highlysuccessful in withstanding vibration and shock tests, was found to bemuch heavier and more expensive to manufacture than to be desired.Further, it was found difficult to de-gas the device due to the need forwelding of parts and the use of nuts and bolts in its construction whichtended to trap gas. Further, it was found difficult to maintain thedistance between the filament and the deflector electrode constant withthe heating of the filaments.

The present invention provides an improvement over the device of theaforementioned patent as well as prior attempts at a ruggedized design,in affording an area cathode in which the structural members of thedeflector electrode are eliminated by forming this electrode on a wallof the casing.

Further, a novel spring tensioning device is embodied in the filamentsupport which is of simple design, yet highly effective in maintainingthe filaments uniformly spaced from the deflector electrode duringheating, at the same time affording a proper resilient support forenabling the filaments to withstand shock and vibration. This end resultis achieved in the device of the present invention with structure whichis of simple and economical design and has a minimum weight.

Referring now to the drawings, FIG. 1 is a cross-sectional view of oneembodiment of the invention;

FIG. 2 is a view illustrating the spring tensioning mechanism of theembodiment of FIG. 1;

FIG. 3 is a cross sectional view taken along the plane indicated by 3-3in FIG. 2;

FIG. 4 is a cross-sectional view showing an alternative embodiment ofaspring tensioning mechanism that may be utilized in the device of theinvention; and

FIG. 5 is a cross sectional view taken along the plane indicated by 5-5in FIG. 4.

Briefly described, the device of the invention is as follows: Adeflector electrode is formed by depositing a thin metallic film on theinner wall of the casing housing the electron gun, which is opposite tothe wall of such casing towards which the electrons are to be directed(for example, the wall on which the display is generated). Thermionicfilaments for generating the 2 electrons are mounted in spacedrelationship to the deposited deflector electrode by means of resilientsupport mounts in the form of spring members which tension the ends ofthe filaments.

Referring now to FIGS. 1-3, one embodiment of the invention isillustrated. Deposited on a wall of casing 11 is a thin metallic film 12which may, for example, be of aluminum deposited by conventional vacuumdeposition techniques. Deposited layer 12 forms a deflector electrodeand extends over the area through which the electron flow is desired, asdescribed in the aforementioned US. Pat. No. 3,769,540. Spaced fromelectrode 12 are a plurality of thermionic strip or wire filaments l4.Positioned between the filaments and electron target 15, which maycomprise a phosphor layer, are a plurality of control plates anddeflector electrodes 17, as described in US. Pat. No. 3,769,540. Theconstruction and operation of the control plates, deflector electrodesand target form no part of the present invention and therefore will notbe discussed further herein. This invention is rather concerned with thestructure for the deflector electrode 12 and the means for supportingfilaments l4.

Filaments 14 are each attached at one end thereof, e.g., by welding, tometallic strip 18 which is attached to posts 20 mounted on a wall ofcasing 11. Casing 11 may be fabricated of glass or ceramic material. Theother ends of the filaments are fixedly attached, as by welding, tometallic strip member 25 which is welded to pins 27, the pins beingfused to casing ll. Fixedly attached to strip 25 as by welding are aplurality of spring members 30. Also attached to strip member 25 is arod 32. Spring members 30 are fabricated of a highly resilient material.such as Inconel 750, and have bent over end portions 30a which arejoined to U-shaped portions 30b at the opposite ends thereof by a linearportion 300. The filaments 14 are spaced from deflector electrode 12 bymeans of rod 32 over which they pass, and are resiliently held in thisposition by virtue of the abutment of end portion 30a of the springmembers thereagainst. it thus can be seen that the filaments areresiliently tensioned to maintain the desired spacing from electrode 12and at the same time are cushioned against shock and vibration by virtueof the spring action of the spring members.

Referring now to FIGS. 4 and 5, an alternative embodiment for the springmembers is illustrated. This second embodiment has the advantage in thatit requires less space laterally for its implementation. In thisembodiment, the rod 32 is eliminated and spring 30 is formed from a pairof generally vertically extending leaf portions 30a and 30b. Leafportion 30a is attached to support strip 25 which is mounted on casing11. Leaf spring portion 300 has a plurality of vertical slots 300 formedtherein and the filaments 14 are placed within one of these slots andfixedly attached to the spring at this point by suitable means such aswelding. The springs are appropriately tensioned to provide the desiredresilient support for filaments 14.

While the device of the invention has been described and illustrated indetail, it is to be clearly understood that this is intended by way ofillustration and example only and is not to be taken by way oflimitation, the spirit and scope of this invention being limited only bythe terms of the following claims.

We claim:

l. in an electron flood gun for providing a uniform flow of electronsover a predetermined area, said gun 3 comprising elongated filamentmeans for generating electrons. flat deflector electrode meansencompassing substantially said predetermined area and proximate to saidfilament means in a first direction therefrom and flat directorelectrode means parallel to said deflector electrode means and proximateto said filament means in a direction therefrom opposite to said firstdirection and towards which the flow of electrons is desired, and acasing, said gun being mounted within said casing, the improvementincluding:

said deflector electrode means being formed on one of the walls of saidcasing, and means for resiliently supporting the filament means inspaced relationship from the deflector electrode means in a planeparallel to said deflector electrode means, said resilient meanscomprising a spring 4 member resiliently tensioning one end of each ofsaid filament means,

said spring members each comprising a bent over portion at one endthereof and further including a rod member fixedly mounted adjacent tosaid spring members, the filament means being passed over said rodmember and resiliently urged against said rod member by the bent overend portions of the spring members.

2. The device of claim I wherein said spring members each include aU-shaped portion at the ends thereof opposite said one end, saidU-shaped portions being fixedly attached to the casing and a linearportion inter connecting said U-shaped portions and said bent overportions.

a e a a

1. In an electron flood gun for providing a uniform flow of electronsover a predetermined area, said gun comprising elongated filament meansfor generating electrons, flat deflector electrode means encompassingsubstantially said predetermined area and proximate to said filamentmeans in a first direction therefrom and flat director electrode meansparallel to said deflector electrode means and proximate to saidfilament means in a direction therefrom opposite to said first directionand towards which the flow of electrons is desired, and a casing, saidgun being mounted within said casing, the improvement including: saiddeflector electrode means being formed on one of the walls of saidcasing, and means for resiliently supporting the filament means inspaced relationship from the deflector electrode means in a planeparallel to said deflector electrode means, said resilient meanscomprising a spring member resiliently tensioning one end of each ofsaid filament means, said spring members each comprising a bent overportion at one end thereof and further including a rod member fixedlymounted adjacent to said spring members, the filament means being passedover said rod member and resiliently urged against said rod member bythe bent over end portions of the spring members.
 2. The device of claim1 wherein said spring members each include a U-shaped portion at theends thereof opposite said one end, said U-shaped portions being fixedlyattached to the casing and a linear portion interconnecting saidU-shaped portions and said bent over portions.